19 june 2018 16:00:05

The effect of wall roughness with different lubricant film thicknesses on the characteristics of adhered fuel films of diesel-n-butanol blending fuels after spray impingement has been investigated. Four steel plates with different types of roughness (root mean square height-Sq) that were coated with different lubricant film thicknesses (hl) were used as impinged walls. The experimental conditions included dry walls (hl = 0), semi-wetted walls (SWW) with different thin oil films (0 < hl/Sq < 1), and fully wetted walls (FWW) with a thick lubricant film (hl > Sq). The results indicate that the adhered fuel mass ratio (ε) of blended fuel with 25% n-butanol (B25) was higher than that of blended fuel with 15% n-butanol (B15) under the same conditions. ε increased with an increase in Sq on the dry walls, but, under SWW conditions, it decreased with an increase in oil film thickness. The fuel film morphology was almost unaffected by the change in Sq, but the results implied that the roughness parameter-Skewness (Ssk) exerted a greater impact. The mean thickness ha and accumulated diameter Dl of the adhered fuel film increased with an increase in hl, but, under FWW conditions, the effect of the roughness on the adhered film’s features was insignificant.